Neurological disease, whether central or peripheral, is an uncommon cause of lameness in the feline patient (Garosi, 2012). However, it must be considered as a possibility when investigations do not reveal an obvious orthopaedic or soft tissue cause.
Lameness relating to neurological disease can be difficult to confirm and localise without advanced investigations such as magnetic resonance imaging and cerebrospinal fluid analysis. A thorough clinical examination, together with radiographic images and an in-depth knowledge of the motor and sensory functions of the peripheral nerves which innervate the limb, can assist with a presumed diagnosis. This can help ascertain the best course of action to take in first opinion practice where advanced modalities are not available, and referral is not an option for the owner.
Examination
Ideally, examination of the feline patient should begin with gait analysis in order to determine which limb(s) is affected, and to identify whether a true lameness is present or whether the patient is monoparetic. Monoparesis is defined as a loss of voluntary motor function in an individual limb as a result of disease or injury to the peripheral nerve or unilateral spinal cord damage.
Gait assessment can be more difficult in feline patients than in canines, as it is less controlled and likely to involve observing the animal moving around the consulting space rather than being able to vary the speed and type of surface that the patient moves on. Asking the owner to video the patient moving in the home environment before the consultation can be useful, as fear and lack of confidence within the veterinary clinic may affect the patient's willingness to move around freely. The observer should note the following:
- Whether the patient is able to fully load the affected limb
- Whether the limb is placed with each stride
- Whether the pattern of gait demonstrated is normal
- Any signs of ataxia or poor control
- Any neurological deficits such as knuckling or scuffing.
Following on from gait assessment, gentle palpation of the neck, back and limbs should take place in order to determine whether the patient demonstrates any change in behaviour or facial expression which may indicate pain, as well as to assess for muscle mass and symmetry. The author would then follow this by assessing the range of motion of each joint of the limbs, visually inspecting the feet for any signs of uneven nail wear and the footpads for cyanosis which could indicate thrombosis, an important differential cause of monoparesis. These signs are likely to be coupled with other clinical signs such as vocalisation. Visual inspection of the face to reveal any signs of asymmetry of the facial muscles or third eyelid is also useful to rule in or out Horner's syndrome as a possibility.
The patient should then be evaluated from a neurological point of view; determining postural reactions and spinal reflexes. Suitable means of assessing postural reflexes in cats include:
- Paw positioning
- Hopping
- Wheelbarrow test
- Tactile placing (Garosi, 2009).
Assessing the postural reflexes in this way may allow any for the detection of any neurological deficits which could not be identified through gait assessment. Deficits in the postural reflexes of more than one limb are likely to indicate a spinal cord lesion rather than a peripheral nerve lesion. Next, spinal reflexes should be evaluated. The spinal reflexes that can be assessed include:
- Withdrawal reflex
- Extensor thrust
- Patellar reflex (Garosi, 2009).
These reflexes may be absent or reduced in a patient with a peripheral neuropathy. Further localisation of which peripheral nerve is affected can be achieved by cutaneous sensory testing, and a knowledge of which muscles and dermatomes are innervated by which peripheral nerves. Loss of sensation of a particular area region of the limb, if it can be identified, can be particularly useful in determining which nerve(s) is or are affected (Risio, 2005).
Causes of peripheral nerve damage
Possible causes of peripheral nerve damage are listed in Table 1. If peripheral nerve injury to the hindlimb is suspected, the two nerves which are most likely to be affected are the sciatic nerve and the femoral nerve (Garosi, 2012). The femoral nerve is protected by the sublumbar musculature and so is less likely to be affected than the sciatic nerve. Sciatic nerve injury is likely to cause the following clinical signs:
- Lameness or monoparesis
- Dropped hock
- Knuckling
- A limb which can still support the patient's body weight as a result of a functioning quadriceps muscle
- Sensory deficits of the lateral, dorsal and plantar surfaces of the foot (Forterre et al, 2007).
Table 1. Possible causes of peripheral nerve damage
| Disease category | Specific condition |
|---|---|
| Neoplasia | Localised nerve sheath tumourLocal invasion or pressure on nerve structure caused by adjacent tumourLymphoma |
| Vascular | Fibrocartilagenous embolismThrombus |
| Inflammatory | Neuritis |
| Traumatic | Plexus avulsionPeripheral nerve injury(Both may be caused by falling from height or road traffic accidents in cats – look for other signs which are suggestive)Iatrogenic damage, which most often occurs during surgery in the femoral region, such as femoral head and neck excision |
| Toxic | Tetanus |
| Degenerative | Spinal stenosisIntervertebral disc disease |
Femoral nerve injury is likely to cause the following clinical signs:
- Lameness or monoparesis
- The inability to load the affected limb
- Carrying the limb in a flexed position
- Loss of stifle extension
- Loss of patellar reflex
- Quadriceps atrophy
- Loss of cutaneous sensation of the medial limb and medial digit (Garosi, 2012).
Treatment
For both femoral and sciatic nerve injury, treatment is supportive. This is likely to include:
- Analgesia where appropriate as compensations may cause pain (Risio, 2005). Compensations arise from overload of the unaffected limbs and increased pressure on other structures of the body such as the spine and neck
- Rehabilitation therapies to reduce oedema and improve circulation, prevent contractures, maintain muscle activity and aid the return of function of the limb through motor and sensory re-education (Sharp, 2012)
- Modification of lifestyle or environment to prevent further injury and enable recovery
- Preventing and treating skin lesions arising from impaired function of the limb.
Case study
Overview and signalment
An 8-year-old male neutered domestic short hair cat was presented for rehabilitation services with a suspected femoral nerve injury. There was no known history of trauma, but he is an outdoor cat and had been outdoors on the day he presented as lame.
History
The cat initially presented to his owner as lame on his right hindlimb following a period of time spent outdoors. Over the next 24 hours, his owner witnessed this progress to ‘dragging’ the affected limb. He was taken to his veterinary surgeon who reported clinical findings which included:
- Weight bearing on the affected limb but limited floor clearance leading to scuffing of the nails
- Dropped right hock
- No obvious pain response during examination
- Delayed proprioception affecting the right hindlimb
- Normal joint range of motion
- No other obvious neurological deficits.
The owner was advised to restrict him to one room, and meloxicam and gabapentin were prescribed. Reassessment was arranged for 5 days from the initial visit.
There was no improvement seen at the revisit appointment, and radiographs under general anaesthesia were arranged. These did not reveal any significant abnormalities. Referral for further investigation was offered but declined, and so the owner was advised to provide crate rest and continue to administer daily meloxicam, initially for 4 weeks, then extended to 6 weeks following no initial improvement. The initial suspected cause of the cat's symptoms was cruciate disease.
The owner elected to seek the second opinion of an alternative first opinion vet with an interest in orthopaedics. No further diagnostic tests were performed, but because of physical examination findings including marked atrophy of the quadriceps muscle and loss of quadriceps function, a diagnosis of femoral nerve injury was suspected, and physiotherapy recommended.
Rehabilitation therapy assessment
The cat was presented for an assessment for rehabilitation therapies 3 months after the initial onset of clinical signs. His owner revealed she had seen some improvement in this time with the cat now able to load the limb despite occasional knuckling and scuffing. At the time of presentation, he was no longer receiving any medication. His assessment revealed the following:
- He was placing his right hindlimb with every step but with poor ground clearance and occasional knuckling (Figure 1) and scuffing
- The cat was reactive on palpation from the mid-thoracic spine through to the lumbar spine, most likely compensatory as a result of increased stress placed on the muscles supporting the spine
- He had mildly reduced shoulder extension bilaterally, but otherwise normal range of motion in all joints of the limbs
- There was marked atrophy of the quadriceps femoris, hamstring muscle group and gluteal muscle of the right hindlimb (Figure 2)
- Muscle tone felt normal
- The cat's hopping reflex was normal, he had normal withdrawal and extensor thrust and no obvious sensory deficits of the right hindlimb
- He has negative paw placement of the right hind foot
- The nails of his right hindlimb were scuffed.
Possible causes of these clinical findings were discussed with his owner, including femoral and sciatic nerve injury. As further investigation was not an option, symptomatic treatment including physiotherapy was recommended, to include a home exercise plan and weekly sessions at the rehabilitation centre. The owner was also advised to contact her vet regarding analgesia to manage the cat's back pain, which was suspected to be compensatory in nature.
Physiotherapy sessions
The physical therapy sessions consisted of treatments detailed in Table 2. While all of these exercises are suitable to include from day 1, the intensity and number of repetitions should be increased gradually over time to ensure the patient is coping; and the patient should be assessed throughout the session for signs of fatigue. In addition, the owner was asked to perform the following home exercise plan on a twice-daily basis. This consisted of:
- Passive range of motion: Moving the joints of the fore and hindlimbs through their available range until natural resistance is met. This exercise improves and maintains joint range of motion and enhances circulation and proprioception
- Sensory massage: Applying very light touch in upward strokes from the toes up to the stifle. Potential benefits include neurological and proprioceptive enhancement.
- Rhythmical stabilisations (described in Table 2)
- Three-legged stands (Figure 5): Lifting each limb in sequence for 10 seconds between each set of stabilisations. This encourages normal loading and functions as a strengthening exercise
- Standing on hindquarters (described in Table 2).
Table 2. Techniques used during physiotherapy sessions
| Physical therapy treatment | Description | Potential benefits |
|---|---|---|
| Soft tissue massage | A combination of effleurage strokes and kneading was applied to the patient's neck, back and limbs | Improved circulationImproved proprioceptive awarenessEased muscle tensionRelease of endorphins to provide analgesia |
| Rhythmical stabilisations (Figure 3) | With the patient standing in a square position (front feet under shoulders and hind feet under hips), the patient's body weight was pulsed on and off the fore and hindquarters | Improved proprioception through stimulating normal limb position and loadingaStrengthening of the postural muscles of hindlimbs |
| Standing on hind quarters | A treat was used to bring the patient into a ‘beg’ position | Loading of hind quartersStrengthening of postural muscles of hindlimbs |
| Walking over a proprioceptive tract | The patient was encouraged to move slowly over a tract made from different textured surfaces including flooring, yoga mat, bubble wrap, vet bed and towel | Enhanced neurological signal through stimulation of sensory receptors in the feetImproved proprioception |
| Cavaletti (Figure 4) | The patient was encouraged to walk over hula hoops placed on the ground | Active range of motion exercise encouraging enhanced flexion and extension of joints of limbsImproved co-ordinationStrengthening |
| Laser therapy | Class IV therapy was administered to the thoracic and lumbar spine | AnalgesiaImproved circulation |
| Pulsed magnetic field therapy | A pulsed magnetic therapy jacket containing coils was placed over the spine and right hindlimb | AnalgesiaImproved circulationStimulation of nerve regeneration |
Response to treatment
Rehabilitation therapy is ongoing at the time of writing, but so far the cat has shown a promising response to treatment, noticeable to both the owner and therapists involved. Improvements seen to date (1 month from starting physiotherapy) include:
- Improved loading of the right hindlimb and placing with every step
- Better floor clearance and a reduction in scuffing and knuckling
- Less angulation through the hock joint at both stance and during gait
- Improved muscle bulk of the right hindlimb.
Treatment plan
The cat's sessions will be continued on a weekly basis for as long as he continues to progress, together with his home exercise plan, both of which will be modified to include an increase in the number of different exercises performed and in the number of repetitions of the exercises being performed already.
The likelihood of recovery is related to the degree of disruption of the nerve following the episode of trauma (Thomas, 2022), and early intervention with physical therapies are likely to be most successful (Risio, 2005). Amputation may be a viable option for patients who show no signs of improvement, or who suffer from complications such as self-mutilation of the limb (Thomas, 2011). The author would suggest trialling treatment for a period of 10–12 weeks before making this decision.
Conclusions
Without a definitive diagnosis, it is difficult to determine whether cats with suspected peripheral nerve injury will show improvement with treatment options available, such as those provided for this cat. Owner commitment, together with preventing further injury and treating pain, are essential elements of treatment and should be discussed with the owner.